As a method of sequentially unloading a multiplicity of cases stacked up on a pallet, hitherto, for example, a method of separating sequentially by one case each by lifting by hand heavy cases containing objects from the top side of the case group stacked up in plural rows on a pallet by a plurality of workers is known.
However, when sequentially unloading a multiplicity of cases one by one by the hands of workers as mentioned above, a plurality of workers should be required for separating case groups stacked up in plural rows on a pallet in a short time, and moreover heavy cases containing objects are lifted by hand from the top stage and separated sequentially, and it takes time and labor for separating case groups in plural rows, and the working efficiency is poor.
Besides, the number of stacks of the case groups stacked up on the pallet is limited to the height that can be separated by the hands of the workers, and still more when separating cases with a smooth side surface such as corrugated cartons, the hands are likely to slip when the case stacked up on the top of the case group is lifted, and it is difficult to lift and separate the heavy case containing objects.